Direct Torque Control of Induction Motor Drive

This paper presents an implementation of direct torque and flux control (DTC) for induction motors and the comparative analysis of DTC with both PI (proportional and integral) and fuzzy logic controller powered by a Voltage Source Inverter (VSI). The switching patterns of the inverter are generated using reference values for controlled flux and electromagnetic torque. The proposed control algorithm makes no distinction between managing the flux in the stator and the rotor. With this control strategy, the operation of an induction motor can be investigated in the same manner as that of a DC motor. The advancement of power electronics and numerical electronics has enabled low-power applications to effectively control an axis at a variable speed. Using these technological advances, the scientific community has developed a number of control strategies for mastering the flux and torque of electrical machines in real time, with Direct Torque Control (DTC) being one of them. DTC operates with remarkable regulatory qualities without requiring rotational speed feedback. This scheme uses only the stator voltages and currents to calculate the electromagnetic torque and stator flux magnitude and motor parameter independent (except for stator resistance). The dissertation describes the traditional DTC scheme in great detail to simulate an induction motor in a stationary d-q reference frame and demonstrate its free acceleration characteristics. The simulation is run with a 3.7kW, 450V, 50Hz induction motor and the standard DTC scheme.